Zoning groundwater quality for agriculture by classification WILCOX index (Case study: Qazvin plain)

Methods for evaluating the quality of groundwater resources and recognition of appropriate locations for urban and agricultural water demand has been known as an important item in water resources planning. In this study, by using geostatistical methods, the chemical properties of groundwater were analyzed for agricultural land use in Qazvin plain. Therefore, 364 samples of groundwater was ingathered, the samples were chemically analyzed in terms of electrical conductivity, and sodium absorption ratio were analyzed. Experiment semi-variogram each parameter was calculated using the GS 늇꫞ and different models were fitted. Then, interpolation was made by kriging and inverse distance (IDW) methods using the GIS software. The results of the methods by RMSE criterion showed that kriging method is superior to the IDW method and interpolation was made by this method. Finally, zonation map of the plain for agriculture was prepared using fuzzy logic and WILCOX graph. According to the final map, 34 percent of the area for agriculture is suitable, 51 percent relatively suitable and 15 percent is unsuitable for this land use. So, we can say that the water quality in the study area is favorable for agriculture.